The present invention, in some embodiments thereof, relates to a digitizer system and/or touch-screen and, more particularly, but not exclusively, to a digitizer system and/or touch-screen that supports stylus detection.
Digitizer systems are commonly used as input devices for a variety of electronic products and for a variety of different applications. Typically digitizer systems allow a user to provide free stylus input with a finger and/or stylus. Some digitizer systems are intended as a general replacement for a mouse as the primary pointing and navigation device for desktop computers.
A touch-screen is a digitizer system that is integrated with an electronic display screen. Touch-screens are often used for operating portable devices, such as Personal Digital Assistants (PDA), tablet Personal Computers (PCs), wireless flat panel displays (FPD) screens, laptop computers, smart phones and other devices. Touch-screens can be used for example to select virtual buttons displayed on the screen, to manipulate size and position of displayed objects, to enter data with a virtual keyboard, virtual number pad and/or by handwritten input, to open a document or application, to scroll within a window, to draw and/or to play games. Touch-screens typically support fingertip detection. Some touch screens additionally or alternatively support stylus detection.
Styluses may be particularly useful for applications that require touch detection with higher resolution such as drawing applications and/or applications that require handwritten input. Some applications are specifically geared toward receiving input from a stylus such as for example security applications that require a user to provide a handwritten signature. At times, usage of a stylus is a personal preference. Known styluses include passive styluses that may be powered by the electronic device and/or active styluses that may be battery powered.
U.S. Pat. No. 7,292,229 entitled “Transparent Digitiser,” assigned to N-Trig Ltd., the content of which is incorporated herein by reference, describes a digitizer with an electronically refreshable display screen for user interaction via an object such as a stylus. The digitizer includes a transparent sensing arrangement of detectors located at the electronically refreshable display screen for detecting an electric field of the object while the object hovers over or touches the digitizer. The object such as the stylus includes a resonator arrangement that is energized in response to receiving an excitation signal from an excitation arrangement of the digitizer.
U.S. Pat. No. 7,372,455 entitled “Touch Detection for a Digitizer,” assigned to N-Trig Ltd., the content of which is incorporated herein by reference describes a digitizer system including a grid of sensing conductors extending over a sensing area, a source of oscillating electrical energy at a predetermined frequency, and detection circuitry for detecting a capacitive influence on the sensing conductors when said oscillating electrical energy is applied, the capacitive influence being interpreted as a touch, e.g. fingertip touch. The digitizer system is advantageous in that the same sensing conductors can be used both for fingertip touch sensing and for detection of an electromagnetic stylus. Another advantage is that the digitizer system can distinguish between more than one fingertip and/or more than one stylus interacting with the digitizer system at the same time.
Japanese Patent Publication No. JP5173698 entitled “Coordinate Reader” describes a coordinate reading which computes a position on which an electromagnetic stylus was put based on a signal picked up by a sense line of the coordinate reader. The coordinate reader includes a plurality of sense lines each of which is formed with a loop coil and also includes a dedicated loop coil for noise detection. The dedicated loop coil for noise detection is shown to be positioned along one edge of the reader that is opposite an edge along which the sense lines connect to circuitry associated with the reader. A subtractor circuit in electrical communication with the sense lines and the dedicated loop coil for noise detection finds a difference between a signal derived from the sense line and a signal derived from the dedicated loop coil for noise detection. Consequently the noise component on the sense line can be removed.